Field of the Invention
The present invention relates to wireless communications, and more particularly, to a method of transmitting a random access preamble in a time division duplex (TDD)-based wireless communication system, and a wireless device using the method.
Related Art
3rd generation partnership project (3GPP) long term evolution (LTE) evolved from a universal mobile telecommunications system (UMTS) is introduced as the 3GPP release 8. The 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in a downlink, and uses single carrier-frequency division multiple access (SC-FDMA) in an uplink. The 3GPP LTE employs multiple input multiple output (MIMO) having up to four antennas. In recent years, there is an ongoing discussion on 3GPP LTE-advanced (LTE-A) evolved from the 3GPP LTE.
In a time division duplex (TDD) system, a user equipment (UE) performs uplink (UL) transmission and downlink (DL) reception in one frequency band. When it is said that the UE supports a half duplex operation, it implies that UL transmission and DL reception are both possible, but only one of the UL transmission and the DL reception can be performed at one time. If the half duplex operation of the UE is guaranteed, an interference between a UL transmission signal and a DL reception signal can be avoided, and a burden of using a full duplex module which is relatively expensive can be decreased.
Recently, multiple serving cells are introduced to provide a higher data rate. In the TDD system, DL/UL configurations may be configured differently between the multiple serving cells, and the UE may receive a service provided from the multiple serving cells.
However, since various DL/UL configurations are configured, there may be a need to restrict UL transmission as to a UE supporting a half-duplex operation.